Avengers: Age of Ultron, released this week, is one of many superhero films destined for the multiplex in the coming months and years. What's behind this trend? And what kind of villain would be powerful enough to stop it in its tracks?

In the fall of 2010, as The Walking Dead was about to debut on TV, I launched my Media Genres: Zombies course at the University of Baltimore and examined what that horror subgenre reflects about our culture…